To reach Gatwick on a budget, take Thameslink from St Pancras, Farringdon, or London Bridge

https://gunnermaya718.trexgame.net/gatwick-airport-railway-station-everything-you-need-to-know-1

To reach Gatwick on a budget, take Thameslink from St Pancras, Farringdon, or London Bridge. Trains are frequent, accept contactless and Oyster, and often cost less than express services.